core/network: avoid endless probing when no network backend is present

core/internal/server/network/manager.go

@@ -1,6 +1,7 @@
 package network
 
 import (
+	"errors"
 	"fmt"
 	"sync"
 	"time"
@@ -10,6 +11,10 @@ import (
 	"github.com/yeqown/go-qrcode/writer/standard"
 )
 
+// ErrNoNetworkBackend is returned when no supported network management daemon
+// (NetworkManager, iwd, systemd-networkd, ConnMan) is present on the system.
+var ErrNoNetworkBackend = errors.New("no supported network backend found")
+
 func NewManager() (*Manager, error) {
 	detection, err := DetectNetworkStack()
 	if err != nil {
@@ -58,7 +63,7 @@ func NewManager() (*Manager, error) {
 		}
 
 	default:
-		return nil, fmt.Errorf("no supported network backend found: %s", detection.ChosenReason)
+		return nil, fmt.Errorf("%w: %s", ErrNoNetworkBackend, detection.ChosenReason)
 	}
 
 	m := &Manager{

core/internal/server/server.go

@@ -3,6 +3,7 @@ package server
 import (
 	"bufio"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -1481,26 +1482,36 @@ func Start(printDocs bool) error {
 	log.Info("")
 
 	go func() {
+		switch err := InitializeNetworkManager(); {
+		case err == nil:
+			notifyCapabilityChange()
+			return
+		case errors.Is(err, network.ErrNoNetworkBackend):
+			log.Warn("No supported network backend present; skipping retries")
+			return
+		default:
+			log.Warnf("Network manager unavailable, will retry: %v", err)
+		}
+
 		ticker := time.NewTicker(30 * time.Second)
 		defer ticker.Stop()
 
-		if err := InitializeNetworkManager(); err != nil {
-			log.Warnf("Network manager unavailable: %v", err)
-		} else {
-			notifyCapabilityChange()
-			return
-		}
-
-		for range ticker.C {
+		for range 10 {
+			<-ticker.C
 			if networkManager != nil {
 				return
 			}
-			if err := InitializeNetworkManager(); err == nil {
+			switch err := InitializeNetworkManager(); {
+			case err == nil:
 				log.Info("Network manager initialized")
 				notifyCapabilityChange()
 				return
+			case errors.Is(err, network.ErrNoNetworkBackend):
+				log.Warn("No supported network backend present; stopping retries")
+				return
 			}
 		}
+		log.Warn("Network manager still unavailable after retries; giving up")
 	}()
 
 	loginctlReady := make(chan struct{})